Tools for bending tubes, pipes and electrical conduits are of a well-known type, usually comprising a one-piece body that has an elongated, downwardly grooved arcuate shoe at its bottom, a hook at its front, and an upwardly projecting handle socket in which a shaft-like handle is removably receivable. The hook is engaged under a length of tubing to be bent, which is held down against a floor or other supporting surface, and bending force exerted upon the handle, transmitted to the tube by means of the hook, curves the tube around the shoe.
Various expedients have been devised for indicating to the person using such a tool, during a bending operation, that a predetermined angle of bend has been obtained. As examples of these, reference can be made to U.S. Pat. Nos. 2,953,048, 2,666,351, 3,718,018, 4,052,881, 4,009,602 and 4,442,695.
One of the relatively few types of bend angle indicators that has enjoyed significant commercial success is disclosed in U.S. Pat. No. 2,932,225. It comprises a spirit level vial mounted on the body of the bending tool in a position to be readily visible to the person using the tool and in a lengthwise orientation such that its indicating bubble is centered when a predetermined bend angle is attained. In most of the popular tube benders that incorporate such spirit level indicators, two of them are mounted on the tube body, oriented to signal, respectively, the attainment of bend angles of 45.degree. and 90.degree., these being the bend angles most frequently needed.
Bending tools with spirit level bend indicators have been produced and sold in substantially high volume for more than a quarter of a century. During all of that long period of time the installation of the spirit level vial or vials to the bender body has been a laborious and time consuming procedure. In the commercial form of such tools, the spirit level vial has been installed somewhat differently than as disclosed in U.S. Pat. No. 2,932,225, in an arrangement whereby the vial was protected by the metal body of the tool while still being visible to the user of the tool during a bending operation. The body of the bender was made as a one-piece casting, usually of aluminum alloy, formed with an elongated pad for each spirit level vial. Each pad had at its top a lengthwise extending arcuate bay or concavity that served as a window through which the vial could be seen after it was installed in the pad. For installing the vial, a hole was drilled lengthwise into the pad from one end of it, communicating with the bay and continuing beyond it. The vial was inserted lengthwise into this hole to have its end portions confined in the pad while the major portion of its length was exposed in the window defined by the junction of the bay with the drilled hole.
Since the spirit level vial that was conventionally used was arcuately curved along its length, the hole that was drilled in the pad had to be oversize, that is, its diameter had to be larger than that of the vial. The vial therefore had a very loose fit in the hole and had to be adjusted and fixed at a correct orientation before it could be sealed into the pad. To this end the tool body was secured in a fixture that held it in an attitude corresponding to the bend angle designated by the spirit level, and a toothpick was pushed into the hole in the pad, wedged between the metal and the vial, and shifted as necessary to center the bubble in the vial. The outer end of the hole was then filled with a viscous or plaster-like cement material to fix the position of the vial in cooperation with a dab of that material which had been placed into the blind end of the hole before the vial was inserted. After the cement had partially hardened the toothpick was withdrawn. As a final step, the hardened plug of cement was painted to match the metal body.
The labor required for such installation required a substantial amount of time and was therefore expensive. As a result, tube benders with spirit level angle indicators sold at a substantially higher price than those without such indicators, but there has nevertheless been a substantial and consistent demand for them, such that many thousands are made and sold every year. In view of this volume, it was obvious that any substantial reduction in the time and effort needed for installing spirit level vials would reduce costs and thus yield increased profits for the manufacturer. What was clearly not obvious was how to achieve this benefit. Certainly the long standing failure to do so was not for lack of incentive, since the manufacture of tube benders is a highly competitive industry.
In the light of the present invention it may appear that there should have been no great difficulty in devising ways or means to reduce the labor needed for installing spirit level vials on tube bender bodies, but in fact the problem of doing so was complicated by the need to satisfy other requirements. The body of a tube bender is conventionally molded in one piece, and there would be little or no advantage in expediting spirit level installation at the cost of sacrificing sturdiness of the body or its capability for being economically molded by means of apparatus comprising a minimum number of relatively movable mold or die elements. In addition, the spirit level vial or vials, being fragile, must be well protected by adjacent portions of the body but must nevertheless be readily visible from above the body. And of course the establishment and maintenance of a precise orientation of each spirit level vial is of the essence.